Sian paid two weeks ago, £360 off the debt she owes. The bailiff has come back this morning and wants the remainder (£340). He said if he did not have it by this afternoon he would be bringing a locksmith to the house to break into the house.
Whether or not this would be legal depends on many factors including what the original debt was for and whether or not the bailiff has made a legal levy.
Bailiffs often use this as a threat with no intention of actually going through with it. Getting a locksmith out costs bailiffs just as much as anyone else.
If bailiffs are given part-payment it encourages them to think they will get the rest with a bit more pressure, so it's a bit of a risky strategy unfortunately.
If by 'tv license' you mean an unpaid magistrates court fine for watching tv without a license then ultimately you can't keep the bailiffs out so your best bet may be just to raise the money if you can.